(1) Field of the Invention
The present invention relates to electromagnetic interference (EMI) filtering and more particularly to an EMI filter adapter for use with a connector plug mounted to an enclosure wall and having a plurality of connector pins protruding therethrough.
(2) Background Art
Many electronic systems are known which emit electromagnetic radiation in their operation. Such radiation is also known, depending on its nature, to affect other electronic systems. In order to control electromagnetic interference between electronic systems government agencies have specified maximum levels of a electromagnetic radiation emissions which may be allowed. These levels must not be exceeded for the equipment to be sold. An optimum method for restricting electromagnetic interference is to totally enclose the interference generating electronic system in a shielded housing thereby restricting all emissions therefrom.
In the area of certain types of systems with widely separated elements such as telephone switching systems, total system enclosure is not possible because subscriber related wiring must leave the system enclosure. In such conditions, allowable levels of emissions have been found obtainable by treating the individual wiring conductors to remove electromagnetic interference traveling on them before the conductors leave the enclosure.
A common way to treat such conductors is to capacitively couple the individual conductors to the enclosure at the point that pass through the enclosure. In this regard, U.S. Pat. No. 4,265,506 to Hollyday is known which teaches a filtered connector assembly for retrofit insertion between a mated connected pair or for use in the original equipment design. The assembly comprises a ground plate having a plurality of filter pin members mounted therethrough, hermaphroditic mounting plates assembled to alternate faces of the ground plate and dielectric insert members received within profile portions of each mounting plate for electrically insulating the filter pin members disposed therein.
U S. Pat. No. 4,215,326 also issued to Hollyday teaches a similar device.
U.S. Pat. No. 4,187,481 to Boutros teaches a filter connector which may be installed between mating connectors of a cable and employs the use multiple feed through capacitors to accomplish EMI filtering. Finally, U.S. Pat. No. 4,264,116 to Gliha Jr. teaches a filter connector with an adapter containing a plurality of feed through capacitors to accomplish EMI filtering.
The above art while operating satisfactorily is seen to teach the addition of EMI filtering by means of the insertion of a filter member in series with the conductors and the employing of expensive feed-through type capacitors.